Sawssan Abdelwahab, who fled Idlib in Syria, walks with her children outside the refugees camp near the Turkish-Syrian border in the southeastern city of Yayladagi February 16, 2012. REUTERS/Zohra Bensemra

Nine million Syrians need help, including nearly 3.5 million who have no access to essential goods and services

(Adds comment by Russian ambassador in paragraphs 10-11)

By Michelle Nichols

UNITED NATIONS, April 29 (Reuters) - The United Nations on Tuesday rejected calls for it to deliver humanitarian aid across borders into Syria without the approval of the government in Damascus, saying such operations would be possible only under a stronger U.N. Security Council resolution.

Dozens of top lawyers from around the world argued in a letter to the United Nations on Monday that there was no legal barrier for the world body to carry out cross-border aid deliveries or support other organizations to do the same.

More than 150,000 people have been killed in Syria's three-year-old civil war. Some 2.5 million people have fled abroad and 9 million people inside the country need help, including nearly 3.5 million who have no access to essential goods and services.

"It's the longstanding and consistent position of the United Nations that consistent with its charter ... the organization can engage in activities within the territory of a member state only with the consent of that government of that state," U.N. spokesman Stephane Dujarric said on Tuesday.

"The only exception is where the Security Council has adopted a binding resolution under Chapter 7 of the (U.N.)Charter, authorizing the organization to act without the government's consent," he said.

A Chapter 7 resolution is legally binding and enforceable with military action or other coercive measures such as economic and diplomatic sanctions. Robust U.N. peacekeeping operations, including those in the Democratic Republic of Congo, South Sudan and Ivory Coast, are generally mandated by the Security Council under Chapter 7.

The 15-member council achieved rare unity to unanimously approve in February a resolution demanding rapid, safe and unhindered aid access, including across borders. The resolution was binding, but not Chapter 7 and not enforceable.

U.N. Secretary-General Ban Ki-moon said last week, however, that none of the warring parties in Syria were adhering to U.N. demands for aid access. In his second monthly report on the implementation of the resolution, Ban demanded the Security Council take action in Syria on violations of international law.

U.N. aid chief Valerie Amos is due to brief the Security Council on Wednesday on the humanitarian situation in Syria.

"It's an exaggeration what he says in this report. So I may have some criticism of the report, not just of the Syrian parties," Churkin told Reuters of his planned statement at Wednesday's council meeting.

STRONGER RESOLUTION UNLIKELY

Aid groups working in Syria say they are frustrated at how the United Nations is handling the world's biggest humanitarian crisis, accusing it of excluding them and withholding information needed for assisting millions in need.

"The primary responsibility for the dire humanitarian situation in Syria lies with the parties in the conflict, they are the ones who have the responsibility," Dujarric said. "How to reach people in the most difficult-to-reach areas is something that our colleagues work on day in and day out."

U.S. ambassador to the United Nations, Samantha Power, told the Security Council on Tuesday Syrian President Bashar al-Assad's government has "wasted valuable time and claimed many more lives" by not implementing the council's resolution.

"We should all be clear about where the fault for this deterioration lies. It is the regime with the stroke of a pen that could allow cross-border assistance to reach millions in need, but it doesn't," she said.

"It is the regime that has coldly integrated the denial of humanitarian assistance into its ever-expanding arsenal of weapons against the Syrian people," Power said.

In the February resolution, the Security Council expressed "its intent to take further steps in the case of non-compliance" with the resolution. But council diplomats said Russia was unlikely to agree to any action, such as sanctions, if Syria's government was found to be at fault.

Diplomats also said Moscow would likely be opposed to a Chapter 7 resolution to allow cross-border aid deliveries without the consent of Assad's government.

Russia, supported by China, has shielded its ally Syria on the Security Council during the war. They vetoed three resolutions that would have condemned Syria's government and threatened it with possible sanctions. (Reporting by Michelle Nichols; Editing by Mohammad Zargham)